Wire with power only when running

[01silverado]

Is there a wire I can tap into that only has power when running. It will be turning on a relay so should not be drawing very much power.
thanks

[MKader17]

There are plenty of ignition wires everywhere in the truck. depends on where you are looking

[RedHeartbeat]

In the fuse block under the hood there are lots of those. They're mainly pink wires. Take a test light and find you one to tap into. If its triggering a relay then the power load will be only about 1 amp.

[01silverado]

Hey Red, I havent been on here in awhile. I am only wanting power when the motor is running. I checked a few early but they were on whenever the key was on.

[RedHeartbeat]

oh, you want the relay that controls the starter, tie into it. The PCM recognises the engine is running and shuts off the circuit for the starter relay. You can use the same control to energize a relay. I've never done it before myself but in theory it should be easy to do. If you try to hit the starter while the engine is running you should not be able to because the relay has been disabled. The same logic that controls that can control a relay in the reverse direction since there are terminals on a BOSCH relay that allows energy through the relay when off and no energy when on.

[01silverado]

I just want power while the engine is running. As soon as I turn the key off the power will turn off. And power will not turn back on until the engine has started running. Is there something like that? I think that made since.

[RedHeartbeat]

makes perfect sense to me. You don't want power to the item unless the engine is running, you could care less if the key is on or not. The only way to do that is you have to detect a tach signal. The PCM is doing that with the starter relay. If the engine is running the starter relay circuit is disabled and keeps you from grinding the starter against an already turning flywheel. You'll have to wire into that logic. Break out a wiring diagram for your truck and follow the starter circuitry. If you can get me a copy of the diagram I can try to figure out the exact wiring for you.


FWIW, the fuel pump relay works along the same logic excepts it energizes for just a few seconds when the key is first turned on and then disables until a crank signal is detected or a tach signal is detected.

[01silverado]

I got you now. Ill give the starter deal a try. thanks